Natural cereals, such as hot oat cereals, have been achieving higher and higher degrees of acceptance by consumers. With respect to oats, this may be due, in part, to the widespread promulgation of the recent medical reports impact of oat bran in providing a healthful lowering of cholesterol components in humans. In addition, the oat is a highly nutritious grain, not only in terms of possessing outstanding water soluble fiber levels, but also in terms of the richness of its protein, mineral, and lipid contents and other nutritive factors.
In view of the increasing appreciation of oat products, it is desirable to improve the efficiency and results of traditional oat groat processing, without adversely affecting the natural wholesomeness of the product.
Consumer standards for high quality products, in terms of both organoleptic and convenience attributes, and in terms of healthful nutritional impact, must be met in the products of very economical processes, in order for the cereal product to survive in the highly competitive marketplace. Moreover, such products when packaged in conventional packaging materials, must be shelf stable, to the extent of remaining in a desirably consumable form, and in a form which is readily prepared by the consumer, during the time after manufacture and prior to the consumption by the consumer.
In the case of grain products, generally, and oat products, specifically, shelf stability is reliant chiefly upon the suppression or avoidance of enzymatic and oxidative reactions which may occur within the grain. To the uninitiated, it may seem straightforward to heat the grain to deactivate the enzymes. However, some kinds of processing have been believed to aggravate these enzymatic and oxidative reactions, and some processing may suppress one, and aggravate the other. Some heat treatments may be just right to suppress the activity of the enzymes, but would accelerate the oxidative rancidity development of the lipid content. Enzymatic reactions, particularly those involving lipolytic reactions, occur relatively slowly at low moisture and low temperatures, and unless the enzymes are inactivated, or removed, these reactions can cause rancidity by the production of high levels of free fatty acids (FFA).
Many samples of raw, undamaged oat kernels, as harvested, contain 3-10% of their fat already in the form of FFA. Usual shelf storage of oats, at 18 degrees C. and at about 13% moisture is reported to involve slow increase of FFA. The rate of rancidity development is reported to be accelerated by higher moisture levels, and by higher temperatures.
Moreover, in spite of natural antioxidant properties in oats, the development of rancidity of oats attributable to oxidation reportedly can occur even more rapidly under low-moisture and high-heat conditions, and oat products subjected to such conditions are reportedly typified by an increase in FFA, as well as by subsequent high peroxide levels. The development of such rancidity is accompanied by an observable deterioration in the organoleptic i.e. sensory, attributes, such as, for example, in the aroma and flavor of the grain.
In addition to aroma and flavor, other attributes such as texture, and convenience of consumer preparation are important in the success of competitive hot cereal products. There are a variety of types of oatmeal, characterized by flake thicknesses, which must be made available, in order to meet consumer preferences, and demands, such as for example Steam Table, Old Fashioned, Quick, and Instant types. These types are a function of flake thickness, and affect the convenience of consumer preparation. Improvements in oat processing should be amenable to the production to all such types of oat flake products.
One of the undesirable characteristics of flaked oat cereals, is the tendency to foam out of the bowl in ordinary microwave preparation. This tendency is particularly acute with the thicker types of oatmeal flakes. With the meteoric increase in the use and availability of microwave ovens, this method of consumer preparation of hot oat cereals has also become increasingly popular. Parents are believed to be increasingly likely to encourage their children to prepare a personal serving bowl of hot oat cereal in the microwave. Hence, it would be desirable to provide improvements in oat processing which result in an oat cereal product which is not particularly sensitive to reproduction of exact conditions such as quantity of water, and does not require the so-called two step method, for successful consumer preparation in the microwave.
The problems associated with stability of oats are discussed in several articles and patents. For example, see the following:
H.F. Martin, FACTORS IN THE DEVELOPMENT OF OXIDATIVE RANCIDITY IN READY TO EAT CRISP OAT FLAKES, published in the JOURNAL OF SCIENCE OF FOOD AND AGRICULTURE, 1958, No. 12, pages 817-854.
Dr. Francis Webster, U.S. Pat. No. 4,413,018, Method for Manufacture of Whole Grain oat Product.
As surprising as it may seem, the heat treatment to which the groats have been subjected for the purpose of inactivating the enzymes does not gelatinize the starch in the oat groats. Even the process of steaming prior to the flaking steps has been found to result in substantially no gelatinization of the starch in grain. This has been determined using traditional methods, i.e. microscopic examination of the starch cells for loss of birefringence, as well by more recently developed methods, e.g. by the use of Differential Scanning Calorimetry (DSC).
Prior-art heat treatments, for the purpose of providing an "instant" type cereal, did not necessarily involve gelatinization of the oat starches to a significant extent. For example, U.S. Pat. No. 2,864,702 involved "toasting" of unhulled oats, and temperatures of up to about 210 Degrees F. and resulted in a product which was ungelatinized (See claims 3 and 4, for example.) Yet, upon being placed in boiling water such products reportedly hydrated quickly.
We have discovered, however, that microwave foamover is a substantial problem during the cooking of raw oat products, using the amount of oats per serving, and the amount of water generally believed to be appropriate.
With the meteoric increase in the use and availability of microwave ovens, this method of consumer preparation of hot oat cereals has also become increasingly popular. Parents are believed to be increasingly likely to encourage their pre-teen and adolescent children to prepare a personal serving bowl of hot oat cereal in the microwave. However, one of the characteristics of certain of the types of heretofore available flaked oat cereals, is the tendency to foam out of the bowl in ordinary microwave preparation, unless considerable care and precision in measuring, timing, etc. is exercised. And, of course, many youthful consumers, and others, are not particularly noted for taking such pains in their routine activities.
It is an object of the present invention to provide a high speed, competitive process for the partial pre-gelatinization of oat groats for use in the manufacture of cut and/or flaked hot oat cereals.
It is also an object of the present invention to provide a method for such pre-gelatinization which results in a shelf stable product which is suitable for consumer preparation in a microwave oven.
It is also an object of the present invention to provide a hot oat cereal which is particularly well suited to consider preparation in a microwave oven.